limestone: Bangor vs. Jasper

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limestone: Bangor vs. Jasper

Postby TAG caver » Feb 8, 2011 3:40 am

I've noticed that in my hometown most of pits I bounce like Hoopers, the Natural Well, and the dozen or so other of my unnamed favorites, all seem to occur at about the same elevation in what I'm told is the "Bangor" formation. I've also noticed that all the horizontal stuff occurs in the "Jasper" layer. My question is why does one layer form almost exclusively one type of cave and the other layer forms a different type?
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Re: limestone: Bangor vs. Jasper

Postby Cody JW » Feb 8, 2011 8:52 am

I have noticed in TAG most notable (not all but most) pits seem to be at about 1000 to 1100 feet above sea level. Also on most big mountains there is a bench about 250 feet up from the valley floor then another about 400 to 500 up from the floor. Most pits seem to be at or near these benches.
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Re: limestone: Bangor vs. Jasper

Postby trogman » Feb 8, 2011 10:27 am

I used to spend a lot of time ridgewalking at ~1000' elev. Then one day I decided to look down around 600-700', thinking if I found anything, it would probably be horizontal. The first thing I stumbled on was a short 40' pit, then a very nice 73' pit with about 650' of passage. Soon after that, I came across a 105' pit, with 120' vertical extent. So I guess you could say my thinking has changed about this subject. I don't know how to tell the different types of limestone from each other; about all I can do is tell you if it's limestone or sandstone.
I think part of the reason I am having good finds at lower elevations is that cavers in the past have focused on the higher areas. I am still perplexed that no one ever found that 105 footer before- it was an open-air pit right in the middle of a bench.
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Re: limestone: Bangor vs. Jasper

Postby BrianC » Feb 8, 2011 1:10 pm

Many cavers are looking for something deep. You can find probably more caves in the 700'-900' elevation, but if you can find limestone up higher like 1000-1300' the chance of something deep is possible.
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Re: limestone: Bangor vs. Jasper

Postby tncaver » Feb 8, 2011 1:47 pm

BrianC wrote:Many cavers are looking for something deep. You can find probably more caves in the 700'-900' elevation, but if you can find limestone up higher like 1000-1300' the chance of something deep is possible.


Yeper. Going even higher will get you even deeper. Ellisons tops out in the Pennington. Although that is a rarity. Bangor limestone near Crossville, TN is an uplifted area that literally stacks two layers of limestone on top of itself which doubles the depth potential of caves in that area.
Elevation there is over 2000 feet. The smokies has limestone at that elevation as well. Some of the deepest
caves in TN are in those two areas.
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Re: limestone: Bangor vs. Jasper

Postby Anonymous_Coward » Feb 9, 2011 11:15 am

TAG caver wrote: My question is why does one layer form almost exclusively one type of cave and the other layer forms a different type?


I was going to try to answer your question, but I think the diagram on page 2 of this pdf will explain it better than I could:

http://www.ese.edu.gr/media/lipes_dimos ... /o/183.pdf

Basically, impermeable layers like the Pennington caprock collect and funnel water to the limestone strata like the Bangor. When this water finds a fracture, it dissolves a vertical pit. When this water hits another impermeable layer like the Hartselle, it must again flow horizontally until it reaches a weakness in the Hartselle or the surface. Wherever the water can get past the Hartselle, it bores another pit into the Monteagle. This can be in cave, or on the surface. This is why you often see a horizontal cave entrance just above a Monteagle Pit. The example that comes to mind is Honeycutt Cave and Pit above Gourdneck Cave. The water then travels vertically until it reaches the chert beds in the St. Louis and Warsaw Formations. The water again has a hard time penetrating deeper, so it then flows horizontally to a spring entrance. This is why the last part of multi-drop caves is often a crawl or borehole with chert nodules and beds like the final crawl in McBrides.

The Hartselle in Northern TAG (Tennessee) is often a very resistant sandstone and you get the pattern shown in Crawford's diagram. However, further south in Alabama and Georgia the Hartselle is a weaker siltstone, that is often penetrated inside the mountain by the vertical water. This is why your big pits like Incredible, Fantastic, and Surprise are in Alabama and Georgia and not in Tennessee.
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Re: limestone: Bangor vs. Jasper

Postby Cody JW » Feb 10, 2011 9:55 pm

One cave that is surprising is Deep Well. If you look at it from the base of the hill it is not far up for a 300 foot pit. When they first found it they short roped the first drop because they had no idea a pit that deep could be so low on the hill. I could see how .If anyone has been there I am sure they were surprised by its location on the hill.
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